Poor adhesion between epoxy-based under-fill materials and copper interconnects may be of concern when used in lead-free packages. Poor adhesion may result in failures during post assembly processes and/or during reliability testing. In some cases, wicking of lead free solders (such as SnAg or SnAgCu, for example) may not occur along an entire surface of an interconnect structure, such as a copper bump for example. This may result in a greater amount of the interconnect structure being exposed, which may then lead to poor adhesion with under-fill materials that may be dispensed during subsequent processing.